CompressorTechTwo - 2010 (Sample)

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the configuration of the vessels with a hypothetical plant built on the basis of the preliminary information (such as pipe size, line connections, equipment data, etc.) indicated in preliminary available documents.

The length among the various components (piping, equipment, etc.) can be tuned to find possible plant resonance and evaluate pulsation resonances and shaking force amplitudes among the various operating conditions and variable lengths of hypothetic plant (for example, piping length between elbows, etc). Exceptions (possible risks) are just limited and local cases such as closed branch lines, by-pass, safety valve lines, etc.

For special cases, performance of pulsation bottles can be adjusted by removable orifices and in very special situations by additional volume located near the existing one. Inter-stage components, including cooler, piping and downstream facilities — especially after coolers — must be sized carefully. Undersized components can cause excessive pressure drop and power loss. Larger facilities and a larger cross-sectional area installed with the intention of decreasing pressure drop can cause significant increase of shaking force and vibration. Pulsation and shaking force studies are necessary to avoid vibration problems in related facilities, especially in piping and cooler. Secondary volumes may be studied to reduce this vibration. However, in some cases this solution cannot reduce vibration, and modifications of the recycle line are required to significantly lower shaking forces.

Pulsation studies and reviews must be performed for all operating conditions as well as all transient operating cases and combinations of pressures, speeds and load steps. A maximum allowable unfiltered (overall) pressure pulsation level at the compressor cylinder flange must also be defined in the purchase order.

Summary

A pulsation and vibration analysis report must include time domain (TD) and frequency domain (FD) simulations, TD plots of key forces and pressure pulsation, dynamic pressure drop, models including mounting details (mounting plate, bolts, localized skid, etc.) and shell flexibility (nozzle connection flexibility), calculated cylinder stretch forces, mode shape of bottles and piping, and compressor stiffness assumption (compressor frame modeled as flexible support).

References

Enzo Giacomelli, Marco Passeri, Paolo Battagli, Mario Euzzor, Pressure Vessel Design for Reciprocating Compressor Applied in Refinery and Petrochemical Plants, Proceeding of PVP Conference, Pressure Vessel and Piping, Denver, Colorado, U.S.A., July 17 to 21, 2005.

Dennis Tweten and Klaus Brun, “The Physics of Pulsations – Part I and II,” COMPRESSORTech Two, November and December 2008.

Shelley D. Greenfeld and Kelly Eberle, “New API Standard 618 ( 5 TH ED.) and Its Impact on Reciprocating Compressor Package Design — Part I, II and III,” COMPRESSORTechTwo, June, July-August 2008.

Brain C. Howes, Shelley D. Greenfield, Guideline in Pulsation Studies for Reciprocating Compressors, Proceeding of IPC 02, 4th International Pipeline Conference, Calgary, Alberta, Canada, Sep. 29 to Oct. 3, 2002.

A. Eijk, J.P.M. Smeulers, L.E. Blodgett, A. J. Smalley, Improvements And Extensive To API 618 Related To Pulsation And Mechanical Response Studies, The Recip – A State of Art Compressor, European Forum for Reciprocating Compressor, Dresden, Nov. 4 to 5, 1999.